Method of manufacturing semiconductor integrated circuit device

ABSTRACT

A semiconductor integrated circuit device capable of stably forming a fuse element that is used to adjust the characteristics of the semiconductor integrated circuit device, and a method of manufacturing the semiconductor integrated circuit device are provided. The thickness of an interlayer insulating film above the fuse element is reduced by using an amorphous silicon layer that is formed by sputtering as a material of the fuse element, and by forming the amorphous silicon layer at the same time as metal wiring is formed. The steady ease of laser trimming processing is thus accomplished in the semiconductor integrated circuit device and the method of manufacturing the semiconductor integrated circuit device.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a semiconductor integrated circuitdevice configured to use a fuse element for laser trimming to adjustelectric characteristics, and a method of manufacturing thesemiconductor integrated circuit device.

2. Description of the Related Art

As a resistance element that is used for a voltage dividing circuit of asemiconductor integrated circuit, a diffused resistor that is amonocrystalline silicon semiconductor substrate implanted withimpurities having a conductivity type opposite to that of thesemiconductor substrate, a resistor formed of polycrystalline siliconimplanted with impurities, or the like is used. In designing the voltagedividing circuit, when a plurality of such resistors is used, theresistors are set to have the same length, the same width, and the sameresistivity. Then, the respective resistance elements are equallysubjected to variations in shape in an etching process in which theshape is determined and to variations in impurity implantation.Therefore, even if the absolute values of the resistance elements vary,resistance ratios between the resistance elements can be maintained at aconstant value.

When the resistance elements having a certain resistance value based onthe same shape and the same resistivity are used in a voltage dividingcircuit, various resistance values are realized through seriesconnection and parallel connection of unit resistance elements 200 suchas resistor groups 201 to 204 in FIG. 2. As described above, the unitresistance elements 200 are resistance elements having the same shapeand the same resistivity, and thus, the high resistance ratios betweenthe resistor groups each including the unit resistance element (s) canbe maintained with high accuracy.

Further, fuses 301 to 304 of, for example, polycrystalline silicon, areformed in parallel with the resistor groups 201 to 204, respectively, soas to be cut by laser radiation from the outside. Depending on whetheror not the fuses are cut by the laser radiation, a resistance valuebetween a terminal 109 and a terminal 110 can be changed as necessary.Then, a voltage corresponding to a divided voltage ratio to a fixedresistor formed between the terminal 110 and a terminal 111 is outputfrom the terminal 110.

The structure of the fuses 301 to 304 used in laser trimming of relatedart is described with reference to FIGS. 3A and 3B.

FIG. 3A is a plan view of the fuses 301 to 304 of FIG. 2 arranged sideby side. Each of the fuses has a laser cutting region in which the linewidth is narrower at the center than at the ends, and has at each end awiring connection region, which is connected to an internal circuit bymetal wiring 8 via a contact hole 7. A laser fuse cutting opening 10 isformed in a region where the fuse elements are cut by laser trimming.

FIG. 3B is a sectional view taken along the line A-A of FIG. 3A. A LOCOSinsulating film 13 is formed on a semiconductor substrate 1 to isolateelements from each other. Laser-cut fuse elements are formed on theLOCOS insulating film 13 to a thickness of 2,000 Å to 4,000 Å from alayer of polycrystalline silicon 5 that is the same layer as the oneused for a gate electrode of a MOS transistor. As illustrated in thesectional view, the thickness in the laser fuse cutting opening 10 isreduced by treating a portion of the insulating film that is right abovethe fuses through dry etching, thereby creating a structure thatefficiently transmits the energy of a laser for melting the fuses. Afterthe dry etching, the portion of the insulating film that is above thefuses has a desired thickness suitable for laser processing.

The fuse material used here is the polycrystalline silicon 5, whichdoubles as the gate electrode of the MOS transistor. Accordingly, in thecase of a semiconductor manufacturing process in which just one layer ofthe metal wiring 8 is formed, only a planarization insulating film,which is formed from boron phosphate silicate glass (orborophosphosilicate glass, BPSG) under the one layer of metal wiring,and a final protective film, which is formed from a silicon nitridefilm, are formed on the fuse elements made of this fuse material. Add tothat the silicon nitride film is removed by etching at the same time apad opening through which a terminal is led out of the semiconductorintegrated circuit is opened, which leaves only the BPSG film having athickness of 1 μm or so above the fuses.

In the case of a semiconductor manufacturing process in which two ormore layers of metal wiring are formed, on the other hand, an interlayerinsulating film 22 made mainly from a silicon oxide film is furtherlayered above a BPSG film 16 as illustrated in FIG. 3B in order toinsulate the metal wiring layers from each other. Assuming that thethickness per layer is approximately 1 μm, the total thickness ofinsulating films above the fuses increases from that in the single-metalwiring layer process in proportion to the number of wiring layersstacked, and easily amounts to a several-μm-thick silicon oxide film.The total thickness of silicon oxide films above the fuses is eventhicker in the case where the final protective film is a two-layer filmthat has a silicon nitride film as the upper layer and a silicon oxidefilm as a layer for relieving stress from the underlying metal wiringlayer.

The total thickness of silicon oxide films above the fuses that is thusthick hinders laser energy for fuse cutting from being spent efficientlyon cutting the fuses, and presents a risk of defective cutting. It istherefore common to avoid defective cutting in laser cutting by reducingthe thickness of the silicon oxide film that is the lower layer as wellas the thickness of the silicon nitride film that is the upper layerthrough dry etching as illustrated in the sectional view of FIG. 3B.

A method of forming these fuses made of polycrystalline silicon and amethod of processing the insulating films above the fuses are disclosedin, for example, JP 10-189737 A.

However, processing laser-cut fuses that are used in a semiconductorintegrated circuit of related art has the following difficulties:

Firstly, in the fuse elements made of polycrystalline silicon thatdoubles as the gate electrode of the MOS transistor, the trend towardthe miniaturization of the semiconductor manufacturing process and theaccompanying increase in the number of wiring layers stacked haveincreased the total thickness of insulating films that are locatedbetween the top surface of the semiconductor integrated circuit and thepolycrystalline silicon fuse elements, which makes it difficult to cutthe fuses by external laser irradiation such as fuse cutting executed toadjust the characteristics of the semiconductor integrated circuit.

The method of removing a given amount of insulating films above thepolycrystalline silicon fuse elements through etching and adjusting theremaining insulating films to a given thickness, by adding a step offorming a photomask on the insulating films and a step of performing dryetching on the insulating films, for the purpose of making it easier fora laser beam to reach the fuse elements, also has a problem in thatfluctuations in the thickness of the remaining insulating films aregreater than when this method is not employed, due to dry etchingfluctuations throughout the wafer plane and between wafers, andfluctuations in the thickness itself of each of the stacked interlayerinsulating films. In fuse cutting that uses a laser, there is generallya trade-off between the thickness of insulating films above the fuseelements and the ease of processing the fuses in which the insulatingfilms that are too thick hinders efficient transmission of the energyand leaves the fuses uncut, and the insulating films that are too thintransmit the energy to layers below the fuse elements and let a basesubstrate be damaged, or allow the fuses to remain melted from thefuses' own heat and to reattach to themselves instead of being sublimed.The insulating films therefore have an optimum thickness range in laserfuse cutting. However, the fluctuations in the thickness of theinsulating films above the fuses described above sometimes exceed theoptimum thickness range, thereby making it difficult to stabilize theease of laser processing.

The amount of laser energy that reaches the fuse elements and theresultant destabilization of laser processing are exacerbated further bythe reflection of an irradiating laser beam at the boundary betweeninterlayer insulating films which increases in number as the number ofinterlayer insulating films stacked rises, and by fluctuations in thedegree of reflection which depends on the condition of the boundary.

The etching mask used to remove the insulating films above the fuses canalso pose a problem by being destroyed and inviting etching damage whensecuring an appropriate etching selectivity of the etching mask withrespect to the etched film is difficult and the amount of the film to beetched away is large. This problem arises also when a stopper film foretching which is proposed in JP 10-189737 A is employed.

In addition, because the polycrystalline silicon layer is formed bylow-pressure chemical vapor deposition (LPCVD), which is performedgenerally at a high temperature of 500° C. to 700° C., a method ofreducing the total thickness of insulating films that are piled on fuseelements by forming the fuse elements after a metal wiring layer that islow in melting point or an interlayer insulating film that uses anorganic film cannot be employed for fuse elements that are made fromthis polycrystalline silicon layer.

SUMMARY OF THE INVENTION

Therefore, it is an object of the present invention to provide asemiconductor integrated circuit device using a fuse element for lasertrimming and a method of manufacturing the integrated semiconductorcircuit device in which the thickness of an insulating film above a fuseis reduced by using a silicon-based film as a fuse material and settinga step of forming the fuse close to a step of forming a final protectivefilm, and fuse cutting with the use of a laser is stabilized withoutneeding a high level of dry etching stabilization control.

In order to solve the above-mentioned problems, according to oneembodiment of the present invention, there is provided a semiconductorintegrated circuit device, including: a semiconductor substrate; aninsulating film formed on the semiconductor substrate; two conductorsmade of metal and disposed at a distance from each other on theinsulating film; a first high-melting point metal film layered on thetwo conductors; and a fuse element made from an amorphous silicon layer,which is formed in a region above the insulating film where the twoconductors are spaced apart from each other, and is configured to covera top surface of the first high-melting point metal film and sidesurfaces of the two conductors.

Further, in the semiconductor integrated circuit device according to theone embodiment of the present invention, a second high-melting pointmetal film, which has the same shape in plan view as a shape of theamorphous silicon layer, is formed under the amorphous silicon layer.

Further, in the semiconductor integrated circuit device according to theone embodiment of the present invention, the semiconductor integratedcircuit device includes at least two metal wiring layers, the twoconductors include a last metal wiring layer, which is the highest layerout of the at least two metal wiring layers, and, above the last metalwiring layer, a protective film is formed.

Further, in the semiconductor integrated circuit device according to theone embodiment of the present invention, the protective film includes asilicon oxide film and a silicon nitride film formed above the siliconoxide film, and the silicon nitride film is removed from above the fuseelement to form an opening.

In order to solve the above-mentioned problems, according to oneembodiment of the present invention, there is further provided a methodof manufacturing a semiconductor integrated circuit device including afuse element, the method including:

forming an insulating film on a semiconductor substrate;

layering on the insulating film a first metal film and a firsthigh-melting point metal film in the order stated;

etching the first metal film and the first high-melting point metal filmto form, in a fuse element region, two conductors in which the firsthigh-melting point metal film is placed on top of the first metal filmand which are spaced apart from each other, and to form a bonding pad ina bonding pad region;

forming an amorphous silicon layer by deposition on the two conductors,the bonding pad, and the insulating film;

forming, in the fuse element region, a fuse element from the amorphoussilicon layer, which is formed in a region above the insulating filmwhere the two conductors are spaced apart from each other, and isconfigured to cover a top surface of the first high-melting point metalfilm and side surfaces of the two conductors;

removing the amorphous silicon layer and the first high-melting pointmetal film from the bonding pad region;

forming, by deposition, over the semiconductor substrate that includesthe fuse element, a protective film in which a silicon oxide filmconstitutes a lower layer and a silicon nitride film constitutes anupper layer; and

removing the protective film from above the bonding pad.

Further, in the method of manufacturing a semiconductor integratedcircuit device according to the one embodiment of the present invention,in removing the protective film, the silicon nitride film is removedfrom above the fuse element.

Further, there is provided the method of manufacturing a semiconductorintegrated circuit device according to the one embodiment of the presentinvention, further including forming a second high-melting point metalfilm by deposition, prior to the forming of the amorphous silicon layerby deposition,

in which, in forming the fuse element, the fuse element is formed in thefuse element region from the second high-melting point metal film andfrom the amorphous silicon layer, which is formed in a region above theinsulating film where the two conductors are spaced apart from eachother, and is configured to cover a top surface of the firsthigh-melting point metal film and side surfaces of the two conductors.

According to the one embodiment of the present invention, a high-yieldsemiconductor integrated circuit device superior in long-termreliability and a method of manufacturing the integrated semiconductorcircuit device are provided in which stable fuse cutting with the use ofa laser is accomplished by forming the fuse element from a silicon-basedfilm and setting the step of forming the fuse element closer to a stepof forming a final protective film than as in related art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B are a schematic plan view and a schematic sectionalview, respectively, of a first embodiment of the present invention.

FIG. 2 is a diagram of an example of a voltage dividing circuit in whichresistor elements are used in combination.

FIG. 3A and FIG. 3B are a schematic plan view and a schematic sectionalview, respectively, for illustrating the structure of a fuse element ofrelated art.

FIG. 4A and FIG. 4B are a schematic plan view and a schematic sectionalview, respectively, of a second embodiment of the present invention.

FIG. 5A and FIG. 5B are a schematic plan view and a schematic sectionalview, respectively, of a third embodiment of the present invention.

FIG. 6A and FIG. 6B are a schematic plan view and a schematic sectionalview, respectively, of a fourth embodiment of the present invention.

FIG. 7 is a schematic sectional view of a seventh embodiment of thepresent invention.

FIG. 8 is a schematic sectional view of an eighth embodiment of thepresent invention.

FIG. 9A to FIG. 9C are process flow sectional views of the seventhembodiment of the present invention.

FIG. 10A to FIG. 10C are process flow sectional views of the seventhembodiment of the present invention that are for illustrating stepssubsequent to the steps FIG. 9A to FIG. 9C.

FIG. 11A to FIG. 11C are process flow sectional views of the eighthembodiment of the present invention.

FIG. 12A to FIG. 12C are process flow sectional views of the eighthembodiment of the present invention that are for illustrating stepssubsequent to the steps FIG. 11A to FIG. 11C.

FIG. 13 is a schematic sectional view of a fifth embodiment of thepresent invention.

FIG. 14 is a schematic sectional view of a sixth embodiment of thepresent invention.

FIG. 15A to FIG. 15C are process flow sectional views of the fifthembodiment of the present invention.

FIG. 16A to FIG. 16C are process flow sectional views of the fifthembodiment of the present invention that are for illustrating stepssubsequent to the steps FIG. 15A to FIG. 15C.

FIG. 17A to FIG. 17C are process flow sectional views of the sixthembodiment of the present invention.

FIG. 18A to FIG. 18C are process flow sectional views of the sixthembodiment of the present invention that are for illustrating stepssubsequent to the steps FIG. 17A to FIG. 17C.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a semiconductor integrated circuit deviceincluding a fuse circuit for laser trimming that has a fuse structurecapable of solving the difficulties encountered in related art withregards to the ease of laser cutting processing, by balancing thestabilization of the thickness of an insulating film above a fuseelement and the use of a fuse element material easily cut with a laser,and a method of manufacturing the semiconductor integrated circuitdevice.

Embodiments of the present invention are described below with referenceto the drawings.

First Embodiment

FIG. 1A and FIG. 1B are a schematic plan view and a schematic sectionalview, respectively, of a first embodiment of the present invention forillustrating an example where a three-metal wiring layer process isused. FIG. 1A relates to fuse elements in which an amorphous siliconlayer 17 is formed by sputtering in place of a polycrystalline siliconlayer that is formed by LPCVD in related art. At the top end and bottomend of each of the fuse elements in the drawing, two conductors areformed from third-layer metal wiring 14 to connect to second metalwiring layer 11, which leads to an internal circuit. A via hole 15 isalso formed at the top end and bottom end of each fuse element toconnect the third metal wiring layer 14 and the second metal wiringlayer 11. The amorphous silicon layer 17 is laid out so as to overlapwell in plan view with the third metal wiring layer 14, which forms thetwo conductors, and with the via hole 15. Though not shown, the firstmetal wiring layer, the second metal wiring layer, and the third metalwiring layer are formed by a common semiconductor manufacturing processfor minute processing. For example, the metal of a conductor used in themetal wiring layers is Al doped with Si or Cu, or is Cu, a barrier metalthat is a high-melting point metal such as Ti or TiN is disposed on thebottom surface of the conductor, and an anti-reflection film made of TiNor the like is layered on the top surface of the conductor. Ananti-reflection film 23 for the third metal wiring layer 14 whichrelates strongly to the present invention is shown in FIG. 1B. Thehigh-melting point metal used is not limited to Ti or TiN, and other Ticompounds can be used.

FIG. 1B is a sectional view of a fuse element 301 taken along the lineA-A in FIG. 1A. The fuse element 301 in this embodiment is provided onthe interlayer insulating film 22 that covers the second metal wiringlayer. A silicon oxide film 24 and a silicon nitride film 25 are stackedon the amorphous silicon layer 17 as a two-layer protective film. Whilethe amorphous silicon layer is formed at the time of forming the lastmetal wiring layer in this example, when to form the amorphous siliconlayer is not limited to the time of forming the last wiring layer, andmay be synchronized with the time when a metal wiring layer below thelast wiring layer is formed.

In the structure of the present invention that is illustrated in FIG.1B, the ends of the amorphous silicon layer 17 which forms the fuseelements are formed so as to be in contact with side surface portionsand top surface portions of the two conductors in order to make theareas of contact between the fuse elements and the wiring large and toachieve a stable contact resistance.

The via hole 15 for establishing contact with the second metal wiringlayer 11 is further formed immediately below the third metal wiringlayer pattern. Electrical connection to the second metal wiring layer 11is made through an embedded metal inside the via hole, such as tungsten,and the wiring is led therefrom to the internal circuit.

Unlike the example of related art in which a polycrystalline siliconlayer is formed prior to a wiring layer forming step, the presentinvention uses a silicon target and sputtering to fabricate fuseelements in the process of forming a metal wiring layer that is not thefirst metal wiring layer, instead of LPCVD, which involveshigh-temperature treatment at 500° C. or higher. Setting the temperatureat which the film for the fuses is formed by sputtering to 200° C. orless avoids damaging the wiring layers and the interlayer insulatingfilms that are already formed. This means that the forming of the fusefilm can be timed with the forming of any of the wiring layers in theprocess of forming multiple metal wiring layers, which is advantageousin terms of the degree of freedom in manufacture process.

In addition, sputtering, unlike CVD, is advantageous when a thin film isformed by deposition, and can easily form a film as thin as 1,000 Å orless by deposition. While plasma CVD or the like is low-temperaturetreatment that can be performed at 500° C. or less and is accordingly amanufacturing method suitable for mass production, there are stabilityconcerns when a film of 1,000 Å or less is formed by plasma CVD or thelike. Sputtering is capable of making the fuse film even thinner whilepreventing damage to the surrounding elements and the underlying layersby decreasing fusion energy of the laser. With the laser energydecreased, dimension margins to absorb laser damage in the planedirection and the vertical direction can be reduced, and the reductionin size of the semiconductor integrated circuit contributes to thelowering of cost.

However, the amorphous silicon layer that is less than 150 Å inthickness generally diffuses into the underlying Al layer duringsubsequent heat treatment around 400° C., such as a plasma CVD step forforming the final protective film, and the contact resistance between Alin a fuse connection portion and the amorphous silicon layer risesmarkedly. The diffusion of the amorphous silicon layer is not a problemabove the Al wiring here because the anti-reflection film 23 made ofhigh-melting point metal such as TiN is left above the third wiringlayer 14 in FIG. 1A and FIG. 1B. The side surfaces of the Al wiring, onthe other hand, are in direct contact with the amorphous silicon layerbut, unlike the top face of the AL wiring, have oxygen and carbonadhering thereto that are by-products of dry etching processing and thatsuppress the diffusion of the amorphous silicon layer into the Alwiring. Structured as above, the amorphous silicon layer that is used inthe present invention is capable of achieving a stable contactresistance with metal wiring by setting the target thickness of theamorphous silicon layer to 150 Å or more, even allowing for a thicknessfluctuation of about 10%.

When an insulator target material is formed into a film by sputtering ona semiconductor substrate, it is difficult to control the electricpotential of the insulator. An amorphous silicon target material to beformed into a film by sputtering as in the present invention istherefore usually doped with an impurity such as phosphorus or boron toraise the impurity concentration and lower the resistivity. For thatpurpose, a target material having a resistivity of, for example, 0.01Ω·cm or less is commonly used to serve as a conductor for the fuseelement. In the case where making the silicon film thin pushes theper-unit area sheet resistance to an unignorable level, the length orwidth of the fuse element is adjusted to accomplish a desired fuseresistance.

A low-resistivity silicon thin film can also be achieved by implantingan impurity through ion implantation or the like after forming ahigh-resistivity silicon thin film that contains no impurities. Thismethod, however, requires heat application in a sufficient amount toactivate the impurity, and cannot avoid damage from the heat to theAl-based wiring layer and the interlayer insulating films. It istherefore difficult to fabricate a low-resistance fuse element from asilicon-based material after metal wiring and interlayer insulatingfilms are formed, by other methods than one in which a target high inimpurity concentration and low in resistivity is prepared and formedinto a film by sputtering as in the present invention.

The laser cutting opening in the example of related art is notparticularly formed in FIG. 1B. The reason is that, because theamorphous silicon layer for use as fuse elements is formed at the sametime as the last metal wiring layer as described above, which means noextra layer in the form of an inter-wiring layer insulating film rightabove the amorphous silicon layer, the final protective film provides athickness suitable for cutting the fuses by a laser. This is equivalentto the single-metal wiring layer process of related art where there isno problem with the ease of laser cutting processing, although there arestill fluctuations in the forming of the silicon oxide film 24 and thesilicon nitride film 25, and, on the other hand, this is free of thefluctuations in the thickness of insulating films above the fuses whichoriginates from fluctuations in dry etching for the opening. Stablelaser processing is accomplished as a result. In addition, this reduceslayout dimension margins that are allowed for in related art, such asmargins for fluctuations in the positioning of a laser cut openingpattern with respect to a laser irradiation spot and margins for thepositioning of the laser cut opening with respect to the metal wiring,and accordingly contributes to a reduction in area required for the fuseelement portion.

Furthermore, forming the laser cutting opening means that the siliconnitride film, which has excellent moisture resistance, is removed fromthat portion, and leads to a chance that moisture may seep into thesemiconductor integrated circuit through the silicon oxide film in theopening to cause deterioration in long-term reliability such as thecorrosion of wiring and changes in characteristics. The first embodimentof the present invention, where the only opening remaining in thesilicon nitride film is a hole having the diameter of the laser that isformed during the laser cutting of the fuse element, has anotheradvantage in that the adverse effect on long-term reliability isminimized.

While the fuse elements in this example are wired by the third metalwiring layer and the second metal wiring layer in the three-metal wiringlayer semiconductor manufacturing process, the same effect can beobtained by forming the fuse elements and wiring of the fuse elementswith the use of the second metal wiring layer and the first metal wiringlayer in the two-wiring layer process. In the case of the single-metalwiring layer semiconductor manufacturing process, the same effect can beobtained by, though not shown, using the first metal wiring layer andhigh-concentration diffusion wiring on the silicon substrate. Thepresent invention is thus applicable to semiconductor manufacturingprocesses of various wiring configurations, from single-wiring layerprocesses to multi-wiring layer processes, and can be said to have ahigh degree of freedom in selecting a semiconductor manufacturingprocess.

As has been described, the first embodiment of the present invention iscapable of providing an inexpensive semiconductor integrated circuitthat achieves high quality by enhancing the stability of laser cuttingprocessing of a fuse element from the level of stability in related artand by thus minimizing a drop in yield and the decline of long-termreliability, and that requires less area for the fuse element and thesurroundings of the fuse element.

Second Embodiment

FIG. 4A and FIG. 4B are a schematic plan view and a schematic sectionalview, respectively, of a second embodiment of the present invention forillustrating an example where a three-metal wiring layer process is usedas in the first embodiment. The second embodiment differs from the firstembodiment in that a laser fuse cutting opening 10 is formed in a laserfuse cutting-scheduled region as illustrated in FIG. 4A. A portion of asilicon nitride film serving as a final protective film that isimmediately above the fuse element 301 is removed by dry etching asillustrated in FIG. 4B, which is a sectional view of the fuse element301 taken along the line A-A in FIG. 4A.

A final protective film that mainly includes a silicon nitride film mayvary in thickness depending on how a semiconductor factory where thesemiconductor integrated circuit device is manufactured is set up, onthe characteristics of the semiconductor process used, and also on whatmaterial, conditions, heat treatment, and the like are used. Forexample, in the case where the last metal wiring layer is formed thickin order to allow a large amount of current to flow, the finalprotective film, which is in contact with the last metal wiring layer,needs to be set even thicker in order to adjust a stress balance betweenthis wiring layer and the protective film. In the case where the finalprotective film above the fuse element is left intact as in the firstembodiment of the present invention and the thickness of the finalprotective film hinders the transmission of a sufficient amount of laserenergy for fuse cutting to the fuse element, it is preferred to securethe ease of laser processing by removing the silicon nitride film, whichis the upper-layer protective film out of the two-layer protective film,as in the second embodiment. In this case, it is easy to satisfactorilyreduce fluctuations in the diminishing of the silicon oxide film, whichis the lower layer out of the two-layer protective film, in the dryetching of the silicon nitride film, which is the upper layer out of thetwo-layer protective film, by setting the etching selectivity withrespect to the silicon oxide film to a ratio of 10:1 or higher, and,unlike the example of related art, increased fluctuations in thethickness of the remaining silicon oxide film do not markedlydeteriorate the ease of laser processing.

As in the example of related art, forming the laser cut opening 10 meansthat a portion of the silicon nitride film serving as the finalprotective film is removed from the opening and leads to a chance ofdeterioration in long-term reliability.

For example, the laser-cut surface of a fuse element is generallyexposed in the opening. If this fuse element happens to be exposed tohigh-temperature moisture that contains an electrolyte such as an ionwhile a high voltage of several tens V or higher is being applied to thefuse element, electrical energy promotes chemical reaction on thelaser-cut surface, thereby causing silicon to bond with oxygen in themoisture, transform into a silicon oxide film, and expand. In the casewhere the expansion stress cannot be absorbed, a crack or a brake can becaused around the fuse element, thereby accelerating the seeping ofmoisture to the inside and letting the erosion advance inward. The fuseelements used in the present invention, however, are thinner than the2,000 Å to 4,000 Å-thick polycrystalline silicon layer of related artwhich doubles as a gate electrode, and is set to a thickness of 150 Å to1,000 Å with the use of sputtering to reduce the area of the cut surfaceof the fuse to ¼ of that in related art or less. The present inventionis accordingly reduced in the area of the laser-cut section where thechemical reaction occurs and can control the degree of stress caused bythe chemical reaction, which gives the present invention an advantageover the example of prior art in that the advance of erosion inward isdecreased.

As has been described, the second embodiment of the present invention iscapable of keeping the ease of laser cutting processing of fuse elementsstable even when the silicon nitride film serving as a final protectivefilm is thick, by forming a laser cutting opening in the finalprotective film, and is therefore reduced in the decline of long-termreliability than in the method of related art.

Third Embodiment

FIG. 5A and FIG. 5B are a schematic plan view and a schematic sectionalview, respectively, of a third embodiment of the present invention forillustrating an example where a three-metal wiring layer process is usedas in the first embodiment.

The third embodiment differs from the first and second embodiments ofFIG. 1A and FIG. 1B in that a second high-melting point metal film 18 islayered under the amorphous silicon layer 17. The two stacked films areformed at once by dry etching processing with the use of the same maskpattern, and therefore have the same shape in plan view, with noparticular difference between the two in the plan view of FIG. 5A.

As illustrated in FIG. 5B, which is a sectional view taken along theline A-A in FIG. 5A, the high-melting point metal film 18 is in contactwith the metal wiring layer 14, which forms two conductors at the endsof the fuse, and with the anti-reflection film 23, which is a layerformed above the metal wiring layer 14 from a high-melting point metalas the film 18 is, to contribute to the reduction of contact resistance.The high-melting point metal film 18 particularly has an effect ofreducing the concern for the diffusion of the amorphous silicon layerinto Al which may occur on the side surfaces of the metal wiring layer14 made of Al, as the anti-reflection film 23 does for the top face ofthe metal wiring layer 14. The high-melting point metal film 18 thuslifts restrictions on making the amorphous silicon layer 17 thin.

The fuse elements in the first embodiment and the second embodiment areformed solely from the amorphous silicon layer. In the case where makingthe amorphous silicon layer thin raises the resistance to an unignorablevalue, or in the case where the semiconductor integrated circuit deviceis sensitive to a difference in resistance value that results fromwhether the fuse element is cut or uncut, putting a film of ahigh-melting point metal such as TiN under the amorphous silicon layer17 lowers the resistance value of the fuse element significantly. Theamorphous silicon layer and the TiN layer are both commonly used asanti-reflection films for metal wiring, and adding this high-meltingpoint metal layer does not bring harmful results or side effects to themetal wiring or the surrounding elements, and does not impair the easeof laser cutting processing. Forming a fuse element from TiN alone inrelated art tends to make the ease of laser cutting processing unstabledue to the high melting point of TiN and the thinness of the TiN film.The present invention, where the two-layer structure made up of an upperamorphous silicon layer and a lower TiN layer is employed so that theamorphous silicon layer absorbs and accumulates the laser energy togenerate heat, has an advantage in that the underlying TiN layer is cutmore efficiently than in related art. In this manner, advantages of ahigh-melting point metal can be taken also when a high-melting pointmetal is used as a fuse element material, without impairing thestability of laser cutting.

As has been described, the third embodiment of the present invention iscapable of providing an inexpensive semiconductor integrated circuitthat achieves high quality by enhancing the stability of laser cuttingprocessing of a fuse element from the level of stability in related artwhile giving the fuse element a low resistance, and by thus minimizingthe decline of reliability, and that requires less area for the fuseelement and the surroundings of the fuse element.

Fourth Embodiment

FIG. 6A and FIG. 6B are a schematic plan view and a schematic sectionalview, respectively, of a fourth embodiment of the present invention forillustrating an example where a three-metal wiring layer process is usedas in the first to third embodiments. In the fourth embodiment, formingthe laser fuse cutting opening 10 in a laser fuse cutting-scheduledregion as illustrated in FIG. 6A is added to the third embodiment, andonly a portion of the silicon nitride film serving as a final protectivefilm that is immediately above the fuse element 301 is removed by dryetching as illustrated in FIG. 6B. FIG. 6B is a sectional view of thefuse element 301 taken along the line A-A in FIG. 6A.

The purpose and effects of the fourth embodiment are the same as thosein the second embodiment, and the fourth embodiment is an application,to the third embodiment, of a mode designed for the case where thesilicon nitride film 25 of the final protective film is thick and thisthickness hinders the transmission of laser energy to the fuse in fusecutting.

Configured as this, the fourth embodiment of the present invention iscapable of keeping the ease of laser cutting processing of fuse elementsstable even when the silicon nitride film serving as a final protectivefilm is thick, by forming a laser cutting opening in the finalprotective film, and is therefore reduced in the decline of long-termreliability than in the method of related art.

Fifth Embodiment

FIG. 13 is a schematic sectional view of a fifth embodiment of thepresent invention as an application of the first embodiment illustratedin FIG. 1A and FIG. 1B which covers the periphery of a fuse element inthe semiconductor integrated circuit device as well. Illustrated in FIG.13 is an example in which a three-metal wiring layer process is used asin the first to fourth embodiments.

In FIG. 13, one of the fuse elements in the first embodiment of thepresent invention described above is denoted by 301. In addition to thefuse element 301, a bonding pad 19 through which electrical connectionto an external terminal is made, an NMOS transistor 401 as an example ofthe internal circuit, and wiring in the surroundings thereof areillustrated in FIG. 13.

The fuse element 301 is formed from the amorphous silicon layer 17 towhich the first embodiment is applied. The third metal wiring layer 14made of Al and the anti-reflection film 23 made of a high-melting pointmetal such as TiN are disposed at the ends of the fuse element 301. Thesecond metal wiring layer 11 connects the fuse element 301 to theinternal circuit from a layered film in which the metal wiring layer 14and the anti-reflection film 23 are stacked, through the via hole 15(the connection is not shown).

The NMOS transistor 401, which is given as an example of the internalcircuit, includes an N-type source/drain region 12, a gate insulatingfilm 9, and a gate electrode 6. The NMOS transistor 401 electricallyconnects to other elements and circuits through the contact holes 7, thefirst metal wiring layer 8, the via vole 15 in the interlayer insulatingfilm 22 that connects the first metal wiring layer and the second metalwiring layer, the second metal wiring layer 11, the via holes 15 inanother interlayer insulating film that connects the second metal wiringlayer and the third metal wiring layer, and internal circuit fine metalwiring 21, which is the third metal wiring layer.

The interlayer insulating films 22 are ones used in common semiconductorprocesses, and are made mainly from a silicon oxide film. The surfacelevelness of the interlayer insulating films 22 is maintained bytreating a tetraethyl orthosilicate (TEOS) film or a spin-on glass (SOG)film with a planarization technology such as etch back orchemical-mechanical polishing (CMP).

Similarly, the first metal wiring layer and the second metal wiringlayer are formed by a common semiconductor manufacturing process forminute processing to have a structure common in such manufacturingprocesses. For example, the metal of a conductor used in the metalwiring layers is Al doped with Si or Cu, or is just Cu. A barrier metalthat is a high-melting point metal such as Ti or TiN is disposed on thebottom surface of the conductor to enhance the ease of contact with theunderlying metal layer or silicon substrate, and also to improve thelong-term reliability of the wiring. An anti-reflection film made ofhigh-melting point metal such as TiN is layered on the top surface ofthe conductor in order to prevent reflection of light that is used inphotolithography processing at the surface of the conductor. In short,the fifth embodiment employs general wiring materials and layeredstructure based on a fine rule of the semiconductor manufacturingprocess used. The common technologies used here are irrelevant to thepresent invention, and details thereof are omitted to show a simplifiedmode in the drawing.

The internal circuit fine metal wiring 21 as the third metal wiringlayer to which the fine rule used for the wiring of the internal circuitis applied, on the other hand, is original to the present invention.Although the metal conductor and barrier metal of the internal circuitfine metal wiring 21 are fabricated by a common manufacturing process tohave a common structure as in the first metal wiring layer and thesecond metal wiring layer, and an anti-reflection film is formed abovethe conductor to be utilized in the forming and processing of the thirdmetal wiring layer, the anti-reflection film is ultimately removed asillustrated in FIG. 13, which makes the internal circuit fine metalwiring 21 different from the third metal wiring layer at the ends of thefuse element 301. This applies to all other third metal wiring layersthan the third metal wiring layer that is used for electrodes at theends of the fuse element 301, which is a characteristic of the fifthembodiment. Removing the anti-reflection film ultimately does notparticularly pose a problem because the anti-reflection film is in placeduring the photolithography processing when the anti-reflection film isneeded.

An anti-reflection film above metal wiring which is used in theprocessing of the metal wiring is generally layered on a metal film madeof Al or Cu right after the metal film is formed as a conductor of themetal wiring by deposition, and the piled layers are both processed atonce by photolithography and dry etching. During the exposure to lightin photolithography, the anti-reflection film prevents light that isreflected at the metal conductor from entering an unintended place andresultant deforming or breakage of the pattern.

The anti-reflection film and the conductor consequently remain as aunitary component after the etching processing in this type ofmanufacturing method. In the present invention, however, all of theanti-reflection film except a portion for the fuse element is removedwhen the fuse element is subsequently processed, thus forming thestructure of FIG. 13.

The fuse element can be fabricated also by a method in which aninterlayer insulating film is formed between the fuse element and thethird metal wiring layer, and a via hole or the like connects the fuseelement and the third metal wiring layer. This leaves theanti-reflection film above all parts of the third metal wiring layer. Inthe present invention, the step of layering the interlayer insulatingfilm and the step of forming the via hole may be omitted by forming thefuse element directly after the third metal wiring layer is formed andprocessed. One of the reasons that the anti-reflection film is notpresent above the third metal wiring layer, except for a portion wherethe fuse element is located, is the manufacturing-related reasondescribed above.

In the bonding pad 19 of FIG. 13 through which electrical connectioninside the semiconductor integrated circuit is led out of thesemiconductor chip, the third metal wiring layer, which is the lastmetal wiring layer the same as internal circuit fine metal wiring 21, isdisposed to connect a bonding wire, and an opening is formed in thesilicon oxide film 24 and the silicon nitride film 25 in a region wherethe silicon oxide film 24 and the silicon nitride film 25 constitute aportion of the final protective film that is immediately above thedisposed third metal wiring layer. Common technologies irrelevant to thepresent invention are used here to create a wiring connection structurefor connecting to the internal circuit beyond the bonding pad, which ismade from the third metal wiring layer. Details thereof are thereforeomitted to show a simplified mode in the drawing.

An anti-reflection film such as a TiN film for the third metal wiringlayer that is used in the bonding pad 19 is removed, as is the case forthe third metal wiring layer 21, which is used as the internal circuitfine metal wiring. This presents the following advantage over relatedart:

Even though the forming and processing of the bonding pad involveslayering an anti-reflection film on the third metal wiring layer for areason connected to the manufacturing process of related art, a portionof the anti-reflection film that is exposed in an opening formed abovethe bonding pad portion in the final protective film is removed when theopening is formed by dry etching, to thereby improve in subsequent stepsthe ease of contact with a testing probe and the adhesion of the bondingwire. Still, the anti-reflection film remains above the metal layer thatis under the final protective film around the opening in the finalprotective film, and a section of the anti-reflection film is exposedfrom the section of the opening in the final protective film. Ti-basedfilms are generally susceptible to oxidation from heat, moisture, andthe like. If a Ti-based anti-reflection film that is exposed is kept incontact with, for example, a water current that is used in dicing for along period of time, the Ti-based film is oxidized and expanded, therebylifting the final protective film. The seeping of moisture to the insidemay consequently be accelerated to induce the corrosion of metal wiringand changes in characteristics, though this does not occur often.

The fifth embodiment of the present invention, where the anti-reflectionfilm is not left above the third metal wiring layer except for a portionwhere the fuse element is located and the anti-reflection film isremoved also from the bonding pad, has an advantage in that poor qualityand the decline of long-term reliability are prevented.

As has been described, the fifth embodiment of the present invention iscapable of providing a fuse element that is superior in long-termreliability and that is reduced in manufacturing cost because steps offorming and processing an additional interlayer insulating film areunnecessary, and providing a semiconductor integrated circuit devicethat includes the fuse element.

Sixth Embodiment

FIG. 14 is a schematic sectional view of a sixth embodiment of thepresent invention as an application of the second embodiment illustratedin FIG. 4A and FIG. 4B which covers the periphery of a fuse element inthe semiconductor integrated circuit device as well. Illustrated in FIG.14 is an example in which a three-metal wiring layer process is used asin the first to fifth embodiments.

The NMOS transistor 401 and wiring in the surroundings thereof, the fuseelement 301, and the bonding pad 19 are illustrated in FIG. 14 as in thefifth embodiment. The structures themselves of the NMOS transistor 401,the bonding pad 19, and the fuse element 301 are the same as the ones inthe fifth embodiment. In the sixth embodiment, an opening is formed inboth of the silicon oxide film 24 and the silicon nitride film 25, whichconstitute a two-layer final protective film, in the bonding pad 19 bydry etching, whereas an opening is formed only in the silicon nitridefilm in a portion of the final protective film that is above the fuseelement. In the case where a final protective film that is thick for amanufacturing-related reason hinders the transmission of a laser usedfor fuse cutting and impairs the ease of laser processing of the fuseelement as described in the second embodiment, a photomask for the fuseopening in the final protective film is prepared and processedseparately from a bonding pad opening mask in this manner.

As has been described, the sixth embodiment of the present invention iscapable of realizing a semiconductor integrated circuit device in whichthe ease of fuse cutting processing is stable even when the finalprotective film is too thick to transmit a laser for fuse cutting, andthe long-term reliability is high.

Seventh Embodiment

FIG. 7 is a schematic sectional view of a seventh embodiment of thepresent invention as an application of the third embodiment illustratedin FIG. 5A and FIG. 5B which covers the periphery of a fuse element inthe semiconductor integrated circuit device as well. Illustrated in FIG.7 is an example in which a three-metal wiring layer process is used asin the first to sixth embodiments.

The NMOS transistor 401 and wiring in the surroundings thereof, the fuseelement 301, and the bonding pad 19 are illustrated in FIG. 7 as in thefifth embodiment. The NMOS transistor 401 and the bonding pad 19 are thesame as the ones in the fifth embodiment. The fuse element 301 is anapplication of the third embodiment and is formed from a layered film inwhich the amorphous silicon layer 17 and the high-melting point metalfilm 18 such as a TiN film are stacked. A layered film in which thethird metal wiring layer 14 made from an Al film or the like and theanti-reflection film 23 made of high-melting point metal such as TiN arestacked is disposed at the ends of the fuse element 301. The fuseelement 301 is connected to the internal circuit from this layered filmthrough the via hole 15 by the second metal wiring layer 11.

The anti-reflection film is layered only on the third metal wiring layerat the ends of the fuse element 301 as in the fifth embodiment. Theanti-reflection film is removed from above the third metal wiring layerof the bonding pad 19 and from above the third metal wiring layer of theinternal circuit, which includes the NMOS transistor 401.

The final protective film, which is the topmost layer and is made up ofthe silicon oxide film 24 and the silicon nitride film 25, has anopening only above the bonding pad 19 in order to lead out a terminal.

As has been described, the seventh embodiment of the present inventionis capable of providing a low- resistance fuse element that is superiorin long-term reliability and that is reduced in manufacturing costbecause steps of forming and processing an additional interlayerinsulating film are unnecessary, and providing a semiconductorintegrated circuit device that includes the fuse element.

Eighth Embodiment

FIG. 8 is a schematic sectional view of an eighth embodiment of thepresent invention as an application of the fourth embodiment illustratedin FIG. 6A and FIG. 6B which covers the periphery of a fuse element inthe semiconductor integrated circuit device as well. Illustrated in FIG.8 is an example in which a three-metal wiring layer process is used asin the first to seventh embodiments.

The NMOS transistor 401 and wiring in the surroundings thereof, the fuseelement 301, and the bonding pad 19 are illustrated in FIG. 8 as in theseventh embodiment. The structures themselves of the NMOS transistor401, the bonding pad 19, and the fuse element 301 are the same as theones in the seventh embodiment. In the eighth embodiment, an opening isformed in both of the silicon oxide film 24 and the silicon nitride film25, which constitute a two-layer final protective film, in the bondingpad 19 by dry etching, whereas an opening is formed only in the siliconnitride film in a portion of the final protective film that is above thefuse element. In the case where a final protective film that is thickfor a manufacturing-related reason hinders the transmission of a laserused for fuse cutting and impairs the ease of laser processing of thefuse element as described in the fourth embodiment, a fuse openingphotomask in the final protective film is prepared and processedseparately from a bonding pad opening mask in this manner.

As has been described, the eighth embodiment of the present invention iscapable of realizing a semiconductor integrated circuit device includinga low-resistance fuse element, in which the ease of fuse cuttingprocessing is stable even when the final protective film is too thick totransmit a laser for fuse cutting, and the long-term reliability ishigh.

Ninth Embodiment

A method of manufacturing the semiconductor integrated circuit device ofthe fifth embodiment is described below as a ninth embodiment of thepresent invention with reference to FIG. 15A to FIG. 15C and FIG. 16A toFIG. 16C.

First, a MOS transistor is fabricated on a semiconductor substrate 1 byforming an element isolation region such as an LOCOS insulating film 13,the gate insulating film 9, the gate electrode 6, and the source/drainregion 12. Formed next are a planarization insulating film such as theBPSG film 16, the contact holes 7 in the BPSG film, the first metalwiring layer 8, the interlayer insulating film 22 above the first metalwiring layer 8, the via hole 15 in the interlayer insulating film 22that connects the first metal wiring layer and the second metal wiringlayer, the second metal wiring layer 11, and the interlayer insulatingfilm 22 above the second metal wiring layer 11 (FIG. 15A).

The first metal wiring layer and the second metal wiring layer areformed by using Al doped with Si or Cu, or just Cu, as the metal of aconductor, disposing a barrier metal that is made of high-melting pointmetal such as Ti or TiN on the bottom surface of the conductor, andlayering an anti-reflection film that is made of high-melting pointmetal such as TiN on the top surface of the conductor. Details on thestructure and forming method of the first metal wiring layer and thesecond metal wiring layer are omitted here. In short, the ninthembodiment employs a common manufacturing method that includes formingthe metal wiring described above, and is not limited to a specialmanufacturing process. The illustration of the ninth embodiment is alsosimplified.

Next, the via holes 15 in the interlayer insulating film 22 that connectthe second metal wiring layer and the third metal wiring layer areformed, and the third metal wiring layer 14 is formed (FIG. 15B).

A common method is employed to form the detailed structure of the thirdmetal wiring layer. The anti-reflection film 23 made of a high-meltingpoint metal such as TiN which is indispensable in the present invention,on the other hand, is specially shown in the drawings. At the time theprocessing of the third metal wiring layer is finished, theanti-reflection film 23 remains layered on all portions of the thirdmetal wiring layer.

The amorphous silicon layer 17, which is a characteristic component ofthe present invention, is layered next over the entire surface of thesemiconductor substrate by sputtering (FIG. 15C).

Photo resist 20 is applied next, and then removed by photolithographyfrom other regions than a fuse element forming-scheduled region (FIG.16A).

With the photo resist 20 as a mask, all portions of the amorphoussilicon layer 17 except a portion for the fuse element are removed bydry etching. At this point, the same mask is used to simultaneouslyremove the remaining high-melting point metal film such as a TiN filmfrom above all portions of the third metal wiring layer except a portionfor the fuse element. In this manner, -only portions of theanti-reflection film in wiring connection portions at the ends of thefuse element remain on the third metal wiring layer.

The silicon oxide film 24 and the silicon nitride film 25 are formednext in order as a final protective film (FIG. 16B).

Lastly, an opening is formed in a portion of the final protective filmthat is above the bonding pad 19 through which electrical connection toan external terminal is made, by sequentially etching the siliconnitride film and the silicon oxide film in this portion through dryetching (FIG. 16C).

As has been described, the present invention employs a manufacturingmethod that adds a step of forming a fuse element after a step offorming the last metal film, and does not use a special film for thefuse element itself, which make the present invention flexiblyapplicable to various semiconductor manufacturing processes.

Tenth Embodiment

A method of manufacturing the semiconductor integrated circuit device ofthe sixth embodiment is described below as a tenth embodiment of thepresent invention with reference to FIG. 17A to FIG. 17C and FIG. 18A toFIG. 18C. The structural difference of the sixth embodiment from thefifth embodiment resides in the openings in the final protective film.The manufacturing method in this embodiment is accordingly the same asthe method of manufacturing the semiconductor integrated circuit deviceof the fifth embodiment in the step of forming components on thesemiconductor substrate 1 up through the interlayer insulating film 22that is above the second metal wiring layer 11 (FIG. 17A), the step offorming the third metal wiring layer 14 with the use of theanti-reflection film 23 (FIG. 17B), the step of forming the amorphoussilicon layer 17 for the fuse element by deposition (FIG. 17C), the stepof patterning resist to process the fuse element (FIG. 18A), the step ofprocessing the fuse element by etching, and the step of forming bydeposition the final protective film that is made up of a silicon oxidefilm and a silicon nitride film.

In the next step where the final protective film is processed, theresist 20 that is patterned is formed first on the silicon nitride film.The resist 20 is a pattern that has openings in places, specificallyabove the fuse element region and above the bonding pad region. Thesilicon nitride film 25 is selectively etched away with this resist 20as a mask, to thereby form the laser fuse cutting opening 10 in the fuseelement region and an opening in the bonding pad 19 regionsimultaneously (FIG. 18B).

Another piece of photo resist and another photomask are used to removeby etching the silicon oxide film only from above the bonding pad 19(FIG. 18C).

The final protective film can be processed by a first processing methodin which the application of the first photo resist for processing thesilicon nitride film, the forming of openings in the first photo resistabove the silicon nitride film, and the removal by etching of thesilicon nitride film are followed by the removal of the first resist,the application of the second photo resist, the forming of openings inthe second photo resist above the silicon oxide film, the removal byetching of the silicon oxide film, and the removal of the second photoresist.

A second processing method may instead be employed to process the finalprotective film. In the second processing method, the first photo resistis not removed after the steps of applying the first photo resist,forming openings in the first photo resist above the silicon nitridefilm, and removing the silicon nitride film by etching are executed, andthe application of the second photo resist, the forming of openings inthe second photo resist above the silicon oxide film, the removal of thesilicon oxide film, and the removal of the first photo resist and thesecond photo resist are executed subsequently. The second processingmethod for the final protective film is advantageous in that removingthe first photo resist and the second photo resist at once in the laststep has an effect of eliminating damage to the silicon nitride film atthe edge of the bonding pad opening, as well as an effect of reducingthe number of manufacturing steps.

In the first processing method for the final protective film, a siliconoxide film residue left in the bonding pad opening due to misalignmentof the opening in the second photo resist is prevented by making theopening in the second photo resist wider than the opening in the siliconnitride film which has already been formed. The silicon oxide film isthen removed by etching with the exposed opening in the silicon nitridefilm as a mask. When the opening is formed in the second photo resist,damage from the etching of the silicon oxide film to the exposed portionof the silicon nitride film in the bonding pad is unavoidable. In thecase where there is a concern that employing the first processing methodmay accelerate the seeping of moisture or the like at the edge of thebonding pad that leads to the decline in long-term reliability, theconcern is eliminated by employing the second processing method toprocess the final protective film.

In the second processing method for the final protective film, theetching of the silicon nitride film is followed immediately by thecovering of the second photo resist. An opening wider than the openingin the silicon nitride film is then formed in the second photo resist asin the first processing method. At this point, the first photo resistunderneath which has been cured by the previous plasma etching treatmentof the silicon nitride film remains as it is, and the cured first photoresist can be utilized as an opening mask in the next step of etchingthe silicon oxide film. Damage to the silicon nitride film from theetching of the underlying layer can thus be prevented.

In the case where the first photo resist utilized in the etching has notbeen cured enough and is easily dissolved by solvents of photo resist,performing UV curing treatment before the second photo resist is appliedis recommended. The UV curing treatment advances the curing to theinside of the first photo resist, thereby making the first photo resisthardly soluble, and eliminates the concern that the pattern of the firstphoto resist may lose shape due to a solvent of the second photo resist.Another effect is that the subsequent removal of the first photo resistand the second photo resist is made easy.

The present invention, which employs the method described above, iscapable of providing a method of manufacturing a semiconductorintegrated circuit device that is superior in long-term reliability andthat is improved in the ease of laser cutting of a fuse element byremoving the anti-reflection film from the bonding pad opening and byavoiding etching damage at the edge of the bonding pad opening.

Eleventh Embodiment

A method of manufacturing the semiconductor integrated circuit device ofthe seventh embodiment is described below as a eleventh embodiment ofthe present invention with reference to FIG. 9A to FIG. 9C and FIG. 10Ato FIG. 10C. The method of manufacturing the semiconductor integratedcircuit device of the seventh embodiment is a manufacturing method inwhich the fuse element used in the fifth embodiment is given a layeredstructure that is made up of an amorphous silicon layer and ahigh-melting point metal as in the third embodiment.

The manufacturing process in the eleventh embodiment is therefore thesame as the one in the previous embodiment in the step of formingcomponents on the semiconductor substrate 1 up through the interlayerinsulating film 22 that is above the second metal wiring layer 11 (FIG.9A), and the step of forming the third metal wiring layer 14 with theuse of the anti-reflection film 23 (FIG. 9B).

Next, the high-melting point metal film 18 made of TiN or the like andthen the amorphous silicon layer 17 are formed by sputtering over theentire surface of the semiconductor substrate to be stacked on top ofeach other (FIG. 9C).

A step of patterning resist to process the fuse element (FIG. 10A) isexecuted next. With the same photo resist as a mask, the amorphoussilicon layer 17 and the high-melting point metal film 18 are processedby etching. In the etching, the anti-reflection film is also removedfrom above the third metal wiring layer in other regions than the fuseelement region by etching with the use of the same photo resist mask.

Thereafter, a step of forming by deposition the final protective filmthat is made up of a silicon oxide film 24 and a silicon nitride film 25is executed (FIG. 10B), followed by a step of removing the finalprotective film from above the bonding pad 19(FIG. 10C). These steps arethe same as the ones in the method of manufacturing the semiconductorintegrated circuit device of the fifth embodiment.

Twelfth Embodiment

A method of manufacturing the semiconductor integrated circuit device ofthe eighth embodiment is described below as a twelfth embodiment of thepresent invention with reference to FIG. 11A to FIG. 11C and FIG. 12A toFIG. 12C. The structural difference of the eighth embodiment from theseventh embodiment resides in the openings in the final protective film.The manufacturing method in this embodiment is accordingly the same asthe method of manufacturing the semiconductor integrated circuit deviceof the seventh embodiment in the step of forming components on thesemiconductor substrate 1 up through the interlayer insulating film 22that is above the second metal wiring layer 11 (FIG. 11A), the step offorming the third metal wiring layer 14 with the use of theanti-reflection film 23 (FIG. 11B), the step of forming by depositionthe high-melting point metal film 18 and the amorphous silicon layer 17for the fuse element (FIG. 11C), the step of patterning resist toprocess the fuse element (FIG. 12A), the step of processing the fuseelement by etching, and the step of forming by deposition the finalprotective film that is made up of a silicon oxide film and a siliconnitride film.

In the next step where the final protective film is processed, thesilicon nitride film 25, which is the upper layer out of the finalprotective film, is removed by etching with the use of the same photoresist from above the fuse element and from above the bonding pad. Thelaser fuse cutting opening 10 and the opening above the bonding pad 19are formed in this manner (FIG. 12B).

Another piece of photo resist and another photomask are used to removeby etching the silicon oxide film only from above the bonding pad 19(FIG. 12C).

As a method of processing the final protective film in further detail,any of the first processing method and the second processing method inthe method of manufacturing the semiconductor integrated circuit deviceof the sixth embodiment can be employed. In the first processing method,the silicon oxide film is removed by etching with the use of the secondphoto resist after the first photo resist is removed. In the secondprocessing method, the first photo resist remains during the removal ofthe silicon oxide film by etching with the use of the second photoresist.

The high-melting point metal in the description given above is notlimited to Ti or TiN, and can be other Ti compounds.

The application of the present invention, which uses the structures andmanufacturing methods described above, is not limited to step-downseries regulators and voltage detectors mentioned in the descriptiongiven above, and the present invention is applicable to every productconfigured to adjust the performance of a semiconductor integratedcircuit by fuse cutting. The present invention can accordingly beapplied to other uses than power management ICs.

What is claimed is:
 1. A method of manufacturing a semiconductorintegrated circuit device comprising a fuse element, the methodcomprising: forming an insulating film on a semiconductor substrate;layering on the insulating film a first metal film and a firsthigh-melting point metal film in the order stated; etching the firstmetal film and the first high-melting point metal film to form, in afuse element region, two conductors in which the first high-meltingpoint metal film is placed on top of the first metal film and which arespaced apart from each other, and to form a bonding pad in a bonding padregion; forming an amorphous silicon layer by deposition on the twoconductors, the bonding pad, and the insulating film; forming, in thefuse element region, a fuse element from the amorphous silicon layer,which is formed in a region above the insulating film where the twoconductors are spaced apart from each other, and is configured to covera top surface of the first high-melting point metal film and sidesurfaces of the two conductors; removing the amorphous silicon layer andthe first high-melting point metal film from the bonding pad region;forming, by deposition, over the semiconductor substrate that comprisesthe fuse element, a protective film in which a silicon oxide filmconstitutes a lower layer and a silicon nitride film constitutes anupper layer; and removing the protective film from above the bondingpad.
 2. A method of manufacturing a semiconductor integrated circuitdevice according to claim 1, wherein, in removing the protective film,the silicon nitride film is removed from above the fuse element.
 3. Amethod of manufacturing a semiconductor integrated circuit deviceaccording to claim 1, further comprising forming a second high-meltingpoint metal film by deposition, prior to the forming of the amorphoussilicon layer by deposition, wherein, in forming the fuse element, thefuse element is formed in the fuse element region from the secondhigh-melting point metal film and from the amorphous silicon layer,which is formed in a region above the insulating film where the twoconductors are spaced apart from each other, and is configured to covera top surface of the first high-melting point metal film and sidesurfaces of the two conductors.
 4. A method of manufacturing asemiconductor integrated circuit device according to claim 1, whereinthe first high-melting point metal film comprises one of a TiN film anda Ti compound film.
 5. A method of manufacturing a semiconductorintegrated circuit device according to claim 3, wherein the secondhigh-melting point metal film comprises one of a TiN film and a Ticompound film.
 6. A method of manufacturing a semiconductor integratedcircuit device according to claims 1, wherein the amorphous siliconlayer is set to have a thickness of 150 Å or more and 1,000 Å or less.7. A method of manufacturing a semiconductor integrated circuit devicethat comprises a fuse element, comprising: forming an insulating film ona semiconductor substrate; layering on the insulating film a first metalfilm and a first high-melting point metal film in the order stated;etching the first metal film and the first high-melting point metal filmto form, in a fuse element region, two conductors in which the firsthigh-melting point metal film is placed on top of the first metal filmand which are spaced apart from each other; forming an amorphous siliconlayer by deposition on the two conductors and the insulating film;forming, in the fuse element region, a fuse element from the amorphoussilicon layer, which is formed in a region above the insulating filmwhere the two conductors are spaced apart from each other, and isconfigured to cover a top surface of the first high-melting point metalfilm and side surfaces of the two conductors; forming an interlayerinsulating film above the first metal film; forming a second metal filmabove the interlayer insulating film; etching the second metal film toform a bonding pad in a bonding pad region; forming, by deposition, overthe semiconductor substrate that comprises the fuse element, aprotective film in which a silicon oxide film constitutes a lower layerand a silicon nitride film constitutes an upper layer; and removing theprotective film from above the bonding pad.